In existing rotating machines, the rotor is supported both axially and radially. This may be done using bearings which are lubricated, magnetic, gas-dynamic etc. A common feature of all these bearings is that the length of the rotor shaft increases. Complex and costly support systems are also a necessity, except in the case of gas-dynamic bearings. Gas-dynamic bearings of the foil type do not require such support systems, but their bearing strength is for the present far less than that required for rotating machines with high output or pressure.
Other hydrodynamic and hydrostatic gas bearings have been proposed and to some extent tested but have not achieved significant popularity. Typical for hydrodynamic bearings, for example a foil bearing, is that their rotation generates a lift which gives bearing strength. In hydrostatic bearings, external pressurisation is carried out using specially formed recesses in the bearings. This bearing type requires separate seals.
Some examples of such bearings are disclosed by EP-Al 1607633, 1619355, U.S. Pat. No. 5,827,042 and WO-Al 97/13084.
Amongst these, EP-Al 1607633 describes a vacuum pump having two screw rotors which are supported by a pair of bearings installed on a pair of shafts. The invention is distinguished by a pair of shaft seals not being in contact with the pair of shafts are mounted between the screw rotors and pair of bearings.
EP-Al 1619355 relates to a steam turbine rotor which is rotatably supported in the longitudinal direction, hi this instance, turbine components provide for chambers being formed around the rotor and are exposed to an inner and outer pressure which are different. The turbine has at least one water-powered shaft bearing component to accommodate the rotor, whereby this component along with the turbine component are sealed one after the another in the longitudinal direction.
U.S. Pat. No. 5,827,042 shows a stuffing box for a centrifugal pump, where a spiral groove is cut on the outer surface of a pair tapered bearing surfaces for the rotor. Barrier-liquid is feed to an entry-mouth in the spiral groove, and the groove generates a pressure in the spiral groove which is high enough to overcome the process pressure.
At last, WO-Al 97/13084 discloses an impeller pump, in which the sealing and bearing unit has two rotor-stator pairs of tapered sleeves having a spiral groove which conveys barrier-liquid from an entry-mouth in an entry-chamber to an exit-mouth in an exit-chamber, providing the unit with mechanical stability, trust support capability, and resistance to vibrations in the unit.
This means that the existing technology provides solutions which are costly, complex, bulky and not particularly reliable.